1. Field of the Invention
This invention relates to player pianos which produce musical tones in response to performance information based on MIDI standard.
2. Prior Art
In the player piano, when a performer (i.e., a human operator who plays the player piano) depresses a key, a damper leaves a string while a hammer rotates to strike the string, so that a musical tone is produced. On the other hand, when the performer engages a key release operation, the damper comes in contact with the string, so that the musical tone is subjected to muting. As described above, generation of the musical tone is performed normally in accordance with a series of operations, as follows:
Key depression.fwdarw.string striking.fwdarw.key release.fwdarw.muting.
At a recording mode, performance information is created based on the aforementioned operations and is recorded. At a reproduction mode, the performance information is read and is used to control a motion of a key. When controlling the motion of the key, a solenoid is excited based on the performance information so that the key is driven. Thus, the hammer rotates to strike the string.
In the field of the electronic musical instruments, "MIDI" (an abbreviation for "Musical Instrument Digital Interface") is known as the interface for transmission of performance information in a form of digital signals. Herein, a MIDI message is represented by serial data whose unit corresponds to one byte consisting of eight bits. The MIDI message is configured by data and a status which designates a kind of the message. The status corresponds to "note-on" representing key depression or "note-off" representing key release.
The performance information of the player piano is normally based on the MIDI standard. An action of the player piano is represented by one MIDI message called an event. So, the performance information is configured by multiple events. A series of operations (or actions), which are expressed as "key depression.fwdarw.string striking.fwdarw.key release.fwdarw.muting", are normally represented using a string-striking event which designates an event that a hammer strikes a string and a key-release event which designates an event that a damper comes in contact with a string. Herein, the string-striking event corresponds to note-on while the key-release event corresponds to note-off.
One event is represented by three bytes as shown in FIG. 13. Namely, one event is configured by a status represented by one byte and data represented by two bytes. `0` is written at a top bit (i.e., first bit) of each of the two bytes representing the data in order to provide distinction between the status and data. A note number which designates a musical scale (or a pitch) is written at a first byte of the data following the status. In addition, velocity information representing a velocity of a key is written at a second byte of the data. Since a first bit of the second byte of the data is automatically set at `0`, remaining seven bits are used to represent the velocity of the key.
Among performance techniques of the pianos, there is provided a special performance technique called "half stroke". In the case of the half stroke, a key release is started before completion of a key depression, in other words, a key release is started before a key is completely depressed to its end position. Or, a next key depression is started in the middle of execution of the key release.
However, the conventional player pianos are not designed in consideration of reproduction of the half stroke that the key depression or key release is performed in a halfway manner. In other words, it is difficult to sufficiently reproduce the half stroke using only the string-striking event and key-release event. The paper of Japanese Patent Laid-Open Publication No. 7-175472 describes the technology for accurate reproduction of the string-striking speed in the player piano, wherein a variety of variations are made with respect to the key depressing operations. Actually, however, it is difficult to bring such a variety of variations on the key depressing operations of the player piano. So, it is possible to provide a proposal that additional information is newly introduced to cope with the variation-type performance such as the half stroke.
However, using the additional information causes several problems. That is, if a status other than the aforementioned status used for representation of the note-on/off is set for discrimination of the additional information, it is impossible to maintain compatibility with respect to the MIDI message.
In the conventional player piano, string-striking information and key-release information corresponding to the note-on and note-off based on the MIDI standard are each represented by seven bits. In the actual performance of the piano, a great change occurs on the velocity of the key in a process of transition from pianissimo to fortissimo. For this reason, the velocity of the key cannot be represented by one byte in some case. In such a case, it is necessary to provide an extension for key velocity information. However, if such an extended information is simply set to a status other than the status used for representation of the note-on/off, the player piano suffers from problems like the aforementioned problems regarding the additional information.